Less pension received from march 2017 till date?

I have retired in march 2017 , in my pension book it is written that I will receive an monthly pension of 38000, but from march 2017 I am receiving only rs 22000 per month. Plz help me in this regard what I have to do. Will I get the areares from march 2017to till date and what I have to do to receive the full pension.